BLOOD-SUCKING INSECTS AND TROPICAL DISEASES. 173 



In length these insects range from about 3 mm. in the case of a small Lipopteno 

 to 12 mm. or nearly half an inch in that of a female Hippobosca camelina. 

 The general coloration is a reddish or yellowish-brown, with the thorax 

 mottled with yellow in the case of Hippobosca. The legs in all species are 

 powerfully developed, and the claws have a secondary process on the under- 

 side to assist the insect in clinging to the hair of the host. The eyes are widely 

 separated in both sexes, and the proboscis consists of a pair of downwardly 

 projecting lobes, between which a slender inner tube can be protruded from 

 the head. 



Life-history. — The mode of reproduction of these flies may be described as a 

 further development of the process seen in the Tsetse-flies. In the case of the 

 genera now under consideration, the larva is retained within the oviduct of the 

 mother, as in Glossina, but on extrusion it is incapable of movement, shows 

 little or no trace of segmentation, and its integument simply becomes chitinised 

 and darkened to form the pupal envelope. The larva of Hippobosca on extru- 

 sion is a white ovoid or globular body, with a black cap at one pole, which 

 speedily becomes almost obliterated by the general chitinisation of the 

 integument. 



Habits of the perfect insects. — The winged members of this group as a rule fly 

 but little, and only for the purpose of moving from one host to another, or 

 from one part of the body of a host to another on being disturbed. When 

 using its legs, Hippobosca often runs sideways like a crab. The flies of this 

 genus, which infest horses and cattle, live chiefly between the thighs, along 

 the perinseum, and under the tail. In India Hippobosca francilloni , Leach (/?. 

 canina, Rond.), which infests dogs, has been found to the number of fifty or a 

 hundred on the necks and chests of pariahs. 



PART II. 



Directions for the Collection of Specimens. 



List of Articles Required. 



An entomologist 's collecting -net. — This can be obtained from any dealer in 

 natural-history apparatus. Any net used for collecting butterflies will do for 

 Diptera ; but, on the whole, perhaps an ordinary umbrella-net will be found 

 the most serviceable. One or two spare net-bags should be taken in case the 

 one in use gets torn. 



Ttco dozen glass-bottomed cardboard pill-boxes (assorted sizes, up to 2\ inches 

 in diameter, packed in nests one inside another). 



* These boxes can be obtained from Messrs. Watkins & Doncaster, 36, Strand, London, 

 W. C; but care should be taken to see that the bottoms— and not the tops, as is often the 

 case — are made of glass. Since the boxes are constructed of cardboard, they are liable in 

 tropical countries to go to pieces in the rains ; and to prevent this they should be covered 

 with j:iconet in the following manner, the important point to remember being that the 

 jaconet must be cut in strips on the cross : — Obtain, say, a square yard of the material, and 

 fold it into a triangle by bringing two opposite corners together. Consider how wide the 

 strips must be, according to the varying depths of the boxes to be covered, and rule them off 

 in pencil by drawing lines parallel to the base of the triangle. Cut up the strips, or if possi- 



